D. A multilateral treaty.
People flocked to the cities in the late 1800's because during this time factories were booming and there was more opportunity in the cities. Therefore the answer is B.
A region deals with one specific place, but a theme can apply in many places.
Answer:
The Iron Curtain was the ideological border separating the European states that embraced democracy and capitalism (the so-called Western Bloc, led by the United States) from the European states that applied communism as their form of government, and were led by the Soviet Union (forming the Eastern Bloc), in the Cold War.
After World War II up to the revolutions in 1989, it formed the dividing line between the market-oriented democratic states in the west and the planned, socialist dictatorships in the east. After Yugoslavia's turn away from the Soviet Union in 1948, Hungary, Romania and Bulgaria isolated themselves from Yugoslavia at their borders in a similar way to that of the "capitalist" states.
